Biological monitoring of cadmium exposure in itai-itai disease epidemiology

Cadmium (Cd) concentrations in blood and urine were significantly higher in itai-itai disease patients, suspected patients and inhabitants in Cd-polluted areas in Japan. Urinary Cd concentrations were mainly related to the body burden of Cd and did not decrease for several years following cessation of Cd exposure. There was a close association between urinary Cd excretion and the occurrence of beta 2-microglobulinuria (beta 2-mg-uria). Probit regression analysis between urinary Cd excretion and, beta 2-mg-uria indicated that the threshold value may be set around 4 micrograms/g creatinine (cr.). Studies on inhabitants in Cd-polluted areas showed that urinary, beta 2-mg levels of more than 1000 micrograms/l or 1000 micrograms/g cr. were irreversible, while increased urinary excretion of beta 2-mg was associated with increased mortality. At present, beta 2-mg in urine is not a suitable indicator for monitoring renal tubular dysfunction in the general population since the significance of slightly increased excretion of urinary beta 2-mg has yet to be clarified.